Process for recovering thallium



NOV. 10, 1936. R, TEATS 2,060,453

PROCESS FOR RECOVERING THALLIUM oFiled July 18, 1934 ffm/Zak; Hydra/rid@Jalufzf ATTORNEY Patented Nov. 10, 1936 PROCESS POB RECOVER-ING THALLIUMltoscoe Tests. Denver, Colo, assigner to Ameri'- can Smelting andltcilning Company, New York, N. Y., a corporation oi' New JerseyApplication Il!! 18. l'1934, Serial-'Nm 735.813 8 Claims. (Cl. 20d-15)with water and dissolved in sulphuric acid. Alter boiling to expelsulphur and hydrogen sulphide, the thalious sulphate solution iseiectrolyzed using duriron anodes and aluminum cathodes, the thalliumbeing deposited as thallium sponge which is pressed, melted and castintoA bars of pure thallium metal. Ii desired the metal may be dissolvedwith C. P. sulphuric or nitric acids with a minimum amount of water andthallous sulphate or thallous nitrate recovered by crys- This inventionrelates to .the separation of thallium from cadmium and provides aprocess by which thallium may be readily extracted from mixtures ofcadmium and thallium and recovered as pure thallium metal.

-The` drawing accompanying the specification and forming a part thereofis a ilow vsheet illustrating the process o! the invention.

In accordance with the invention, the metal 10 comprising cadmium andthallium is treated with hot water, preferably in conjunction withsteam, with the result that the bulk of the thallium is converted tothallous hydroxide in solution. The small amount o! cadmium whichentersthe solution is precipitated as carbonate and the their lium inturn precipitated from the cadmium-free solution as thallium sulphidewhich is converted to thallous sulphate in solution and subjected toelectrolysis for the recovery oi thallium.

More specifically the invention may be practised as follows: cadmiumcathodes containing from 5%` 1.020% thallium are placed in a suitabletank, digested with boiling water, the water drained on. steam passedinto the tank and the treatment repeated, say ten to twenty times. 'Ihewash waters are combined and contain most of the thallium and verylittle oi' the cadmium v originally present in the cathodes.

The thallous hydroxide solution is then placed in an agitator tank andsodium carbonate added in suilicient quantities to precipitate thecadmium as cadmium carbonate which is removed by iiltratlon. The cadmiumcarbonate is then dissolved in acid orspent electrolyte and electrolyzedusing insoluble anode and cadmium cathodes and in the presence otsuitable addition agents to yield pure cathode cadmium.

Thallium is then precipitated from the impure thallous carbonatesolution as thallium sulphide. as by sodium sulphide and the precipitatewashed tallization.

While certain novel features of the invention have been disclosed andare pointed out in the annexed claims, it will be understood thatvariousomissions, substitutions and changes may` be made by those skilled inthe art without departing from the spirit of the invention.

What' is claimed is:

l. The 'process for recovering thallium from cadmium-thallium cathodeswhich comprises extracting the thaliium as thalious hydroxide solutionby treating the cathodes'with hot water and steam, precipitating cadmiumtherefrom, pre.

cipitating thallium from the cadmium-free solution as thallium sulphide,converting said sulphide to thallous sulphate in solution and relutionby electrolysis.

y covering thaiiium from the thallous sulphate so thereby recovering thethallium las thallous hydroxide in solution.

3. The process for treating cathodes of cadmium and thallium whichconsists in dissolving out the thallium by repeatedly and alternativelysubjecting said cathodes to the action of hot water and steam.

r noscoE mrs.

